Bright nickel plating



Patented Apr. 14, 19 53 BRIGHT NICKEL PLATING Arthur H. Du Rose, Euclid, Ohio, assignor to The Harshaw Chemical Company, Cleveland, Ohio, a corporation of Ohio No Drawing. Application January 29, 1947, Serial No. 725,166

31 Claims.

This invention relates to electrodeposition of nickel and more specifically to electroplating solutions adapted to produce semi-bright, or, in some cases, fully bright, electrodeposits of nickel, that is, semi-bright or fully bright, as deposited, without the necessity of buffing or polishing.

The principal object of the invention is to provide a process of and solutions for producing semi-bright deposits of nickel which are at the same time ductile, easily buffable, resistant to corrosion and capable of improved coverage of imperfections in the base metal. A further object of the invention is to produce a fully bright deposit, which however is less ductile than the semi-bright deposits. Still other objects will become apparent as the description proceeds.

I have now discovered that by addition of a small quantity of coumarin or any one of certain derivatives of coumarin to nickel plating solutions of the sulfate, chloride, fluoborate and sulfamate types I am able to produce increased brightness which although it is accompanied by some increase in hardness, nevertheless remains I ductile, resistant to corrosion, unusually effective in covering scratch marks, and very easily buffable. These results are obtained without the necessity for using any other brightening addition agents although other brightening addition agents may be used to advantage where increased brilliance is required and increased hardness can be tolerated. coumarin may be used in concentration of from 0.05 to 0.50 gram per liter of solution or to complete saturation, but I preferto use a concentration of from 0.2 to 0.25 gram per liter. Substituents may be alkyl or acyl groups not exceeding four carbon atoms, halogen, hydroxy or carboxy groups. Coumarin sulfonic acids are unsatisfactory since they produce deposits which exhibit poor power to cover scratch marks and poor buffability as compared with coumarin. They do produce deposits having a degree of brightness but since they contain sulfur which decreases resistance to corrosion and reduces ductility, I prefer to use coumarin or some of the other derivatives of coumarin which give results substantially equivalent to those secured by the use of coumarin itself. Cyano coumarins also fail to give the excellent scratch hiding power and buffability and I prefer not to use them. The 514b$fituent group or groups may be in As stated above, any of the hydrogen atoms is replaceable by an alkyl, acyl, chloro, hydroxy or carboxy group. To illustrate but a few of the compounds thus "indicated, the following structural formulae are set forth by way of example -methyl coumarin '3 acetyl coumarin G-chloro coumarin 0 H3 4,8-dimethyl coumarin G-methyl coumarin Mixtures of the above indicated preferred addition agents can be used with good results. Any derivative of coumarin may be expected to be at least fairly satisfactory if it is soluble in the bath to the extent of at least about .05 gram per liter and if the substituent group or groups are inert in the solution or approximately so, for example, nickel or cobalt salts of coumarin carboxylic acids. Concentration of addition agents dissolved in the bath may vary within the limits of solubility but preferably should not exceed one and one-half grams per liter. Examples of substituted coumarins and the preferred concentration and pH ranges of plating solutions according to the invention are as follows:

Cone. of Addition Preferred Optimum Agent R lnge R i ge Pre- Llmlt ferred Coumarin 2. -5. 0 3. 4. 5 .05-.5 25 4 Methyl coumarin 2. 5-5. 0 3. 5'4. 5 1-Sat. (1.0) 9 6 Chloro coumarin 3. 0-5. 0 4. 5-4. 5 .OG-Sat. (.25)- .2 3 Acetyl coumarin 2. (l5. .0 3. 5-4. .5 ,lSat. (.7) .3 Coumarin-3-car- 3.0-5.0 3.5-4.5 0.4-Sat. (1.3).. .7

boxylic acid. 4,8;Dimethyl couma- 2. 55. 0 3. 5-4. 5 .15-Sat. (.6) 4

IIn. 7-Hydroxy coumarin. 2. 0-5. 5 3. 5-4. 5 .1l.5 4

The temperature may be suitably of the order of 120 F. to 150 F.

Wetting agents such as sodium lauryl sulfate or alkyl aromatic sulfonates may be used to eliminate pitting.

The bath may be buffered by boric acid, formic acid or other usual buffers. When one of the compounds appearing in the above table is the only brightening addition agent employed, the resulting electrodeposit is easily buffed, has good scratch covering power and may be termed semibright since it is not usually as brilliant as the deposit which can be produced when a suitable auxiliary brightening addition agent of the aromatic sulfonate type is employed. Even though the brilliance of such deposits is not of as high order as when the auxiliary brightener is employed, it is nevertheless useful and even very much preferable for some purposes. It is suitable, for example, for plating automobile bumpers which readily lend themselves to buffing operations and for which the bright nickel processes have not been adopted commercially. The use of semi-bright nickel according to the present invention on articles which are to be buffed greatly reduces the cost of buffing as well as the amount of metal removed in the bufiing process and imparts high scratch covering power.

It has been stated above that deposits according to the present invention exhibit certain superior properties. Deposits made from the solution shown in Example I have been measured by roughly quantitative tests and have been thus compared with grey nickel deposits and deposits from commercial semi-bright solutions. The bath according to this invention compares very favorably with the others in respect to the ability to hide scratch marks after buffing to full brightness. Three scratch marks of varying depths were made on each panel using weights on the stylus so that corresponding scratches were of comparable depths on all the panels, the panels were then plated and buffed and the number of scratch marks still visible was noted. If a scratch mark was partially hidden, it was rated as visible, half hidden or hidden, whichever seemed closer. On the average, grey nickel showed about 1.6 scratch marks while the deposit from the solution of Example I showed on the average about 0.5 of one scratch mark. The commercial semi-bright solutions (proprietary) ran from about 1.4 to about 2.2. Similarly coverability of polishing marks on the base metal which were of various but undetermined depths was rated on an arbitrary but roughly quantitative basis by visual estimation and the results were what would be expected from the above described determina tions of scratch marks.

One of the factors of buifability is the drag of the bufing wheel against the work. That is, how much does the operator have to pull against the work to overcome the drag of the buffing wheel? This drag was measured and found to be for deposits from the bath of Example I less than half that of grey nickel deposits and of the same order of magnitude as the commercial semibright deposits. Deposits according to the in vention are intermediate in hardness between grey nickel and the commercial semi-bright nickels tested, the hardness range being in the order of six, fourteen, eighteen for grey nickel deposits, deposits according to the invention and the commercial semi-bright deposits tested. In addition to the foregoing, the deposits according to the invention were more lustrous, than other semi-bright deposits, and lost less metal upon buffing to full brightness than other deposits, only about two-thirds as much as the nearest commercial semi-bright and only about one-fifth as much as grey nickel.

If it is desired to produce extreme brilliance, I may also employ as an auxiliary brightener aromatic sulfonates, sulfonamides or sulfonimides such as the naphthalene mono-, di-, and tri-sulfonates, saccharin, naphthalene and benzene sulfonamides and sulfonimides, benzene monoand di-sulfonates and the like. The naphthalene sulfonates may be used in concentration of from 3 to 5 grams per liter. If desired a higher concentration up to saturation may be used but it is not essential. isaccharin does not require as high a concentration as naphthalene sulfonates. It may be used in concentration from 1 to 3 grams per liter. Again, a greater concentration, up to saturation can be used but is not necessary. The benzene sulfonates should preferably be used in somewhat greater concentrations, for example, from 2 grams per liter to 10 grams per liter, 5 to 10 grams per liter being preferable. A greater concentration of benzene mono-sulfonate or ben- 'zene di-sulfonate may be used up to saturation but is not essential.

The following table indicates the preferred range of compositions of electroplating solutions in which coumarin or its above indicated derivap I I 6 TABLE I [Preferred concentration ranges in grams per liter-.1

' Sulf t sillafalte Clliggailde gi Flufigtofiate slllfBgltlll-tlate Nisommo 100-400 160-300 0-120 N1C12.6H20 100-350 30-150 Niuslm 40-120 H1303 1540 -40 15-40 HBF4- to pH 2-4 Ni(SO3NHg)- Wetting Agent 0.1-1 0.1-1 0.1-1 0 1-1 Auxiliary Brightener L 010 0-10 0-10 0-10 1 For example, sodium alkyl sulfates having from 8 to 18 carbon atoms in the molecule and alkyl aromatic sulfonates having from 2 to 12 carbon atoms in the alkyl group 01 groups.

I For example, naphthalene mono-, diand tri-sulfonates, benzene monoand disulfonates and saccharin.

Example I 7 Example V 20 i NiSOLGI-IZO g 300 K180451120 NlC12.6I-I2O g 40 N1C12.6H2O g 40 0 H3303 40 Ziggy 155F 11 sulfate n g 0 5 Sodium.1aury1 sulfate 4 methyl coumarin 0:9 coumarm T 25 H2O to make one liter H2O to make one hter pH 3 5 pH 3.5 Temperature F..- 140 gergpera'ture Ag 5: g: C. D. A. S. F 50 The deposit is similar to that obtained from This solution by comparative tests gives a de- Example I. posit which buffs very easily and in such a man- Example VI her that base metal imperfections are camoufiaged to a large extent. The deposit is semi- "2 2g bnght- Head; '11:: I "'2' 40 Example H Sodium lauryl sulfate g 0.5. 6 chloro coumarin g 0 .21 N1(BF4)2 g 300 Nism'sHzo 30 E20 to make one liter H3303 g 40 10 PH Coumarin 25 Temperature F" 140 c D A s F Sodium lauryl sulfate g 0.5 H2O to make one liter v The. deposit is similar to that obtained from pH 3.5 Example I. Temperature F 14 5 Example VII D NiSO4.6H2O 300 The deposit from this bath is similar to that gigs-g "2-- 2g obtained from Example Sodium lauryl sulfate g 0.5 Example III 50 3 acetyl coumarin g 0.2 H2O to make one liter N1(BF4)2 g 300 pH 3 5 N1C12-6H2O 30 Temperature F 140 213303 40 c. D. A.s.F- 50 oumarin 0.25 sodium lauryl sulfate i 0.5 The deposit is similar to that obtained from .HzO to make one liter Example pH 3.5 Example VIII Temperature F 140 NiSQ 6HzO= g 300; C. D. .A-S-F 100 NiClaGI-IzO g 40 HsBOs g 40 The deposit from this bath 1s similar to that sodium lauryl sulfat from Example Coumarin-B-carboxylic acid g 0.8 Example IV I 113-1210 to make one liter 3 5 N SO3N 2 2 g 150 Temperature F 140 31303 1 i 1 f g 03g 0. D. A-S.F 50

0 mm aury su a e g coumarin 25 The deposit is similar to that obtained from H2O to make one liter p e pH 4.0 Example IX Temperature F 120 s t C D. A. s F 30, N s04- 2O g' 300' NiC12.6H2O' g 90 The deposit is Similar to that obtained from HaBO3- g 40 Example I. Sodium lauryl sulfate g 0.5

Coumarin g 0.25 Naphthalene dlsulfonate g 4 H2O to make one liter pH 2.8 Temperature F 140 C. D. A. S. F..- 80

The deposit from the above solution is bright and ductile.

Example X NiSOcfiI-IaO g 300 NiClz.6H2O g 40 H3303 g 41) Sodium lauryl sulfate g 1 4,8-dimethyl coumarin g 0.4 H20 to make one liter pH 4 Temperature F 130 C. D. A. S. F 50 This bath produces a bright deposit otherwise similar to that of Example I.

Example XI NiSO4.6H2O .g..- 3001 NiClzfiI-IzO g 40 H3BO3 g 40 Sodium lauryl sulfate g 1 Coumarin g 0.3 Benzene mono-sulfonate g E20 to make one liter pH 3.2 Temperature F 130 C. D A. S. F 30 This bath produces a bright ductile deposit.

This application is a continuation-in-part of copending application Serial No. 620,852, filed October 6, 1945, now abandoned.

Having thus described my invention, what I claim is:

1. A nickel plating solution essentially consisting of an aqueous, acid solution of nickel material supplying nickel ions and an addition agent dissolved in said solution and capable of imparting to electrodeposits produced therein improved smoothness and buffability, said solution essentially consisting of a composition of the class consisting of aqueous solutions of nickel sulfate, aqueous solutions of nickel sulfate and nickel chloride, aqueous solutions of nickel fiuoborate, aqueous solutions of nickel fluoborate and nickel sulfate and aqueous solutions of nickel sulfamate and said addition agent being selected from the class consisting of coumarin and its substitution products wherein a substituent of the class consisting of alkyl radicals containing not more than four carbon atoms, acyl radicals containing not more than four carbon atoms, and chlorine, hydroxyl and carboxyl groups replaces a hydrogen atom of the coumarin, such addition agent being dissolved in said solution in concentration from 0.05 gram per liter to saturation.

2. A nickel plating solution according to claim 1 wherein said addition agent is coumarin and is present to the extent of from 0.05 to 0.50 gram per liter.

3. A nickel plating solution according to claim 1 wherein said addition agent is 4-methyl coumarin and is present to the extent of from 0.1 to 1.0 gram per liter.

4. A nickel plating solution according to claim 1 wherein said addition agent is 6-chloro coumarin and is present to the extent of from 0.06 to 0.25 gram per liter.

5. A nickel plating solution according to claim 1 wherein said addition agent is 6-chloro coumarin and is present to the extent of from 0.06 to 0.25 gram per liter, the pH of said solution being from 3.0 to 5.0.

8. A nickel plating solution as defined in claim 1 wherein said nickel material is:

Grams per liter NiSQ4.6I-I2O 160 to 300 NiC12.6H2O 30 to 150 9. A nickel plating solution as defined in claim 1 wherein said nickel material is:

Grams per liter NiSO4.6H2O 160 to 300 NiC12.6HzO 30 to 150 and said addition agent is coumarin, in concentration from 0.05 to 0.50 gram per liter and the pH of said solution is from 2.0 to 5.0.

10. A nickel plating solution as defined in claim 1 wherein said nickel material is:

Grams per liter NiSO4.6H2O 160 to 300 NiClaGI-IzO 30 to 150 and said addition agent is a-methyl coumarin in concentration from 0.05 to 0.50 gram per liter and thepH of said solution is from 2.5 to 5.0.

11. A nickel plating solution as defined in claim 1 wherein said nickel material is:

Grams per liter NiSO4.6H2O 160 to 300 NiC12.6I-I2O 30 the benzene and naphthalene sulfonamids and their salts.

13. An electroplating process comprising passing current from a nickel anode to a cathode through a plating solution according to claim 1. 14. An electroplating process comprising passing current from a nickel anode to a, cathode through a plating solution according to claim 1 wherein said addition agent is coumarin.

15. A nickel plating solution essentially consisting of an aqueous, acid solution of nickel material supplying nickel ions and an addition agent dissolved in said solution and capable of imparting to electrodeposits produced therein improved smoothness and buffability, said solution essentially consisting of a composition of the class consisting of aqueous solutions of nickel sulfate, aqueous solutions of nickel sulfate and nickel chloride, aqueous solutions of nickel fluoborate,

I aqueous solutions of nickel fiuoborate and nickel sulfate and aqueous solutions of nickel sulfamate and saidaddition agent being a mono-chloro coumarin.

16. An electroplating process comprising passing current from a nickel anode to a cathode through a plating solution according to claim 15.

17. A nickel plating solution essentially consisting of an aqueous, acid solution of nickel material supplying nickel ions and an addition agent dissolved in said solution and capable of imparting to electrodeposits produced therein improved smoothness and buiiability, said solution essentially consisting of an aqueous solution of nickel sulfate and nickel chloride and said addition agent being coumarin.

18. A nickel plating solution essentially consisting of an aqueous, acid solution of nickel material supplying nickel ions and an addition agent dissolved in said solution and capable of imparting to electrodeposits produced therein improved smoothness and bufiability, said solution essentially consisting of an aqueous solution of nickel sulfate and nickel chloride and said addition agent being a mono-chloro coumarin.

19. An electroplating process comprising passing current from a nickel anode to a cathode through a plating solution according to claim 17.

20. An electroplating process comprising passing current from a nickel anode to a cathode through a plating solution according to claim 18.

21. A nickel plating solution according to claim 1 wherein said addition agent is 3-chloro coumarin.

22. An electroplating process comprising passing current from a nickel anode to a cathode through a plating solution according to claim 1 wherein said addition agent is 3-chloro coumarin.

23. A nickel plating solution according to claim 1 wherein said addition agent is 6-methyl coumarin.

24. An electroplating process comprising passing current from a nickel anode to a cathode through a plating solution according to claim 1 wherein said addition agent is 6-methyl coumarin.

25. A nickel plating solution essentially consisting of an aqueous, acid solution of nickel material supplying nickel ions and an addition agent dissolved in said solution and capable of imparting to electrodeposits produced therein improved smoothness and buffability, said solution essentially consisting of:

Grams per liter NiSOrfiI-IzO 160 to 300 NiClaGHzO 30 to 150 and said addition agent being 3-chloro coumarin.

26. An electroplating process comprising passing current from a nickel anode to a cathode through a plating solution according to claim 25.

27. A nickel plating solution essentially consisting of an aqueous, acid solution of nickel material supplying nickel ions and an addition agent dissolved in said solution and capable of imparting to electrodeposits produced therein improved smoothness and buffability, said solution essentially consisting of:

Grams per liter NiSO4.6H2O 160 to 300 NiCl2.6I-I2O 30 to 150 and said addition agent being G-methyl coumarin.

28. An electroplating process comprising passing current from a nickel anode to a cathode 10 through a plating solution according to claim 2'7.

29. A nickel plating solution essentially consisting of an aqueous, acid solution of nickel material supplying nickel ions and an addition agent dissolved in said solution and capable of imparting to electrodeposits produced therein improved smoothness and buifability, said solution consisting of aqueous solutions of nickel sulfate and nickel chloride, said addition agent being coumarin and being dissolved in said solution in concentration from 0.05 gram per liter to saturation, and further characterized by the inclusion therein of an aromatic sulfonate auxiliary brightening addition agent of the class consisting of saccharin and benzene sulfonamides.

30. The method of increasing the smoothness, scratch-hiding power and buffability of nickel electrodeposits produced from nickel plating solutions of the class in which the preponderance of the deposited nickel is derived from the presence in the bath of at least one nickel compound of the class consisting of nickel sulfate, nickel chloride, nickel fluoborate and nickel sulfamate which comprises adding to such bath in concentration from 0.05 gram per liter to saturation an addition agent selected from the class consisting of coumarin and its substitution products wherein a substituent of the class consisting of alkyl radicals containing not more than four carbon atoms, acyl radicals containing not more than four carbon atoms, chlorine, hydroxyl and carboxyl groups replaces a hydrogen atom of the coumarin.

31. A nickel plating composition comprising essentially an aqueous, acid nickel sulfate-nickel chloride solution containing, dissolved in the solution, from 0.05 gram per liter to saturation, of an addition agent selected from the class consisting of coumarin and its substitution products wherein a substituent of the class consisting of alkyl radicals containing not more than four carbon atoms, acyl radicals containing not more than four carbon atoms, and chlorine, hydroxyl and carboxyl groups replaces a hydrogen atom of the coumarin, to enhance the smoothness of the plate deposited from such composition.

ARTHUR H. DU ROSE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,818,229 Lutz et al Aug. 11, 1931 2,029,387 Pine Feb. 4, 1936 2,196,588 Hull Apr. 9, 1940 2,198,267 Lind et al Apr. 23, 1940 2,198,268 Lind et a1 Apr. 23, 1940 2,233,500 Westbrook Mar. 4, 1941 2,238,861 Lind et al Apr. 15, 1941 2,326,999 Lind et al Aug. 17, 1943 FOREIGN PATENTS Number Country Date 529,825 Great Britain Nov. 28, 1940 OTHER REFERENCES- Ser. No. 351,241, Weiner (A. P. 0.), published May 18, 1943.

Metal Finishing, April 1940, pages 206 to 210, and August 1940, pages 429 to 432. 

1. A NICKEL PLATING SOLUTION ESSENTIALLY CONSISTING OF AN AQUEOUS, ACID SOLUTION OF NICKEL MATERIAL SUPPLYING NICKEL IONS AND AN ADDITION AGENT DISSOLVED IN SAID SOLUTION AND CAPABLE OF IMPARTING TO ELECTRODEPOSITS PRODUCED THEREIN IMPROVED SMOOTHNESS AND BUFFABILITY, SAID SOLUTION ESSENTIALY CONSISTING OF A COMPOSITION OF THE CLASS CONSISTING OF AQUEOUS SOLUTIONS OF NICKEL SULFATE, AQUEOUS SOLUTIONS OF NICKEL FLUOBORATE, CHLORIDE, AQUEOUS SOLUTIONS OF NICKEL FLUOBORATE, AQUEOUS SOLUTIONS OF NICKEL FLUOBORATE AND NICKEL SULFATE AND AQUEOUS SOLUTIONS OF NICKEL SULFAMATE AND SAID ADDITION AGENT BEING SELECTED FROM THE CLASS CONSISTING OF COUMARIN AND ITS SUBSTITUTION PRODUCTS WHEREIN A SUBSTITUENT OF THE CLASS CONSISTING OF ALKYL RADICALS CONTAINING NOT MORE THAN FOUR CARBON ATOMS, ACYL RADICALS CONTAINING NOT MORE THAN FOUR CARBON ATOMS, ANC CHLORINE, HYDROXYL AND CARBOXYL GROUPS REPLACES A HYDROGEN ATOMS OF THE COUMARIN, SUCH ADDITION AGENT BEING 0.05 GRAM PER LITER TO SATURATION. 